


Pipsqueak & Stutterbug

by NoelleLilacNotte, Yiiiiikes



Series: An Alien, a Xenophile, and Her Brother Walk Into a Bed [2]
Category: Invader Zim
Genre: Blackmail, Brother/Sister Incest, Coercion, Consensual Incest, Cousin Incest, Creampie, Dead Dove: Do Not Eat, Explicit Rape, F/M, Incest, M/M, Pregnancy Scare, Sibling Incest, Species swap au, age gap, an extremely fucked up piece of fiction, getting caught, seriously
Language: English
Status: Completed
Published: 2020-02-27
Updated: 2020-02-27
Packaged: 2021-02-28 07:28:34
Rating: Explicit
Warnings: Rape/Non-Con, Underage
Chapters: 1
Words: 4,278
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/22919962
Author URL: https://archiveofourown.org/users/NoelleLilacNotte/pseuds/NoelleLilacNotte, https://archiveofourown.org/users/Yiiiiikes/pseuds/Yiiiiikes
Summary: An extremely dark spinoff of A Study In Human Biology.What if Zim and his sister DID get caught?
Relationships: Tallest Red/Reader, Tallest Red/Zim, Zim/Reader
Series: An Alien, a Xenophile, and Her Brother Walk Into a Bed [2]
Series URL: https://archiveofourown.org/series/1647340
Comments: 4
Kudos: 31





	Pipsqueak & Stutterbug

**Author's Note:**

> Ok if you somehow missed the tags, here’s your last warning. 
> 
> THIS FIC IS DARK. VERY VERY DARK. 
> 
> If that’s your thing, great! If not, back away slowly.

Christmas wasn't necessarily Zim's favorite holiday, but it was definitely in his top five. If not for all of the presents and the food and the stupid movies he could mock, mercilessly, then for his sister. She insisted on dressing nicely for any and every family occasion, even when Zim was going in skinny jeans and a hoodie.

That was one thing he loved about her. She never hesitated to go against the grain when she wanted to. Of course, that applied to more than just dressing nicely. Much, _much_ more. 

Like for example the fact that she was currently kissing her brother, almost entirely naked in bed with him.

It hadn’t taken a lot of convincing for Zim’s pajama pants to get shoved down off his hips. The pair were alone, together, in the dark. There wasn’t much else Zim could ask for, simply being alone with his one-and-only.

Not that he particularly _minded_ her hand reaching into his boxers, but that wasn’t the only reason he was enjoying himself.

Maybe it was just snow and winter on his mind, but Zim couldn’t help thinking his beloved sister looked like an angel in her white nightgown. Even if she was anything but pure on the inside, the street lights glinted off the snow outside, and framed her face like a glowing halo.

She was beautiful, and she loved him. In that moment, everything was perfect.

But nothing ever really goes right for Zim, now does it?

That damned attic door creaked open and in came Red. 

Zim's cock was still hard in his sisters hand, she had only stopped jerking him off when Red ascended to the top of the stairs.

"Woah, what do we have here? You guys still so afraid of the dark that you gotta share a bed?" He teased. For a moment, Zim was relieved. Red hadn't caught on to what they were doing which meant that they were safe.

And then they weren't. 

"Ugh why are you guys so sweaty? It smells like- ohhh my God. No fucking way. Are you two seriously? Ha!" Shit shit shit. Zim's stomach dropped. His sister hadn't moved, still frozen in fear, hand wrapped around his cock.

Then Red yanked the blanket away, unveiling their sins to the world.

“Holy shit, Purple was right about you two! Ha, hah, oh my god.”

Zim and his sister panicked, the latter immediately falling off of their shared mattress and onto the floor, shrinking away from Zim like he was made of hot lava. But the damage had been done, and Red kept laughing the entire time Zim and his sister frantically redressed themselves, insisting that it wasn’t what it looked like. 

But who were they kidding? They’d been caught. Red had seen Zim with his hard cock dripping precum on his sister’s hand, and there wasn’t an explanation for that. 

Every horrible nightmare Zim had ever had about getting found out was coming true, and he could feel his heart hammering in his chest. It was getting hard to breathe, a staticky black void of fear creeping up his spine. 

It only got worse when Red closed and _locked_ the door behind him.

“So tell me, how long have you two little freaks been getting it on?”

Zim caught eyes with his terrified sister, both of them silently asking whether or not they should tell him the truth.

"It's the first time we've done this, I swear." She said unconvincingly. 

"Bullshit. You know what? I'll make it a little easier for you. When did you kiss for the first time?" 

In the back of his mind Zim recognized how strange it was for Red to be asking questions. To be interrogating instead of screaming to aunt Miyuki or their parents.

"We were eleven." Zim answered quietly.

"Oh come on, you're gonna have to give me more detail than that!" Red chided. It was only then that Zim spotted the barely there bulge in his cousins pajama pants.

“W-we were...we got s-stuck in a broom closet at school. S-some kids shoved us in cuz...cuz they thought it’d be funny.”

“Nice one. Wonder why me and Pur never thought of that.”

“I-I was fre-freaking out and...and Zim kissed me...cuz it was the only thing to distract me f-from it.”

“Aww. That’s cute, real cute. Just a sweet little story about a couple _sick little perverts_ in love.” Said Red, teasingly. He shoved his hands into his pockets and rocked back and forth on his feet, clearly enjoying watching his cousins squirm. 

“Hey, Stutterbug,” Red said, addressing the younger of his cousins. He was still laughing after every other word. “You ever suck his dick?”

"O-only a coup-only a couple times." She said, and Zim noticed the tears welling up in her eyes. He reached out to comfort her but thought better of it and retracted his hand.

"No, no, go ahead! Make her feel better, Zim. Comfort your _sister_. Maybe giving her a kiss will help." Zim looked between his humiliated sister and his cruel cousin but didn't make any move to do anything. "That wasn't a request, freak, kiss her. Now." Red commanded. 

Zim's sister wiped her eyes and gave him a look. He'd always been able to tell what she meant even with just a single expression.

_Just do what he says._

Zim leaned in and kissed her. It was nothing fancy or special, just a still, lingering kiss on the lips. When he tried to pull away, Red stopped him.

"Come on, you call that a kiss? That's pathetic! Use your tongue!" He insisted. It was then that Zim noticed his cousins hand moving in his pocket. What the hell was he—oh.

_Oh._

Zim wanted to snap at Red and call him a filthy pervert and a bastard, but he knew that he was no better.

"Kiss her neck, yeah like that. Now, Stutterbug, why don't you tell me about the first time you sucked your dear old brother off?

“W-we...um...we’d gone to different classrooms for...uh...for sex ed.”

“Pfft! You would be that fucking repressed. Let me guess, he saw those shitty diagrams and creamed his pants!” 

“Zim would NEVER—!”

“Shut it, Pipsqueak. Let’s give _her_ the chance to speak for once.”

“A-and after, we snuck off...to the, uh, the b-bathroom. Cuz...no cameras?”

“Holy shit you’d been _looking_ for places to fuck in public? Damn, you’re sicker than I thought.”

“N-no! Well, kinda...but we, I, um...”

“Just get to the good bit.”

“I sucked him off in the bathroom, ok?!” She whisper-screamed, forcing the words out as quickly as she could.

"What did I say earlier about _more detail?_ " Tell me a story Stutterbug! I wanna feel like I was _there_." Red said. He was hardly even trying to hide the fact that he was jacking off. Zim's sister had seemed to notice it too, as she refused to look at him when she spoke.

"I uhm... I texted him a-and I told him that I couldn't stop thin-thinking about- thinking about his dick and I- an' I wanted it in my mouth." She said, tugging at a loose thread on her nightgown.

"Pipsqueak, you sure seem invested in the story." Red nodded at Zim's still half hard cock. "Why don't you show your sweet little sister just how good of a storyteller she is?" 

Zim knew exactly what Red meant but that didn't stop him from squeaking out an angry "what?!"

"Jeez, you're so dumb you can't even pick up on context clues. Take your dick out and jerk it while your sister talks about blowing you." Red commanded.

Zim shivered, both in discomfort and arousal. He yanked off his haphazardly angled shorts, resisting the urge to push his knees together and cover himself with his hands.

Red snickered, reveling in the embarrassed blush creeping up his cousins’ faces. 

“Hey, Stutterbug, do you swallow?”

“I...I-I uh...um...”

“Tch, of fucking course you clam up on us now. Hey Pipsqueak, you tell me. Does your little sister swallow when she sucks you off?”

“... _yes_.” Responded Zim, voice barely a whisper.

“Heh, _nice_. Maybe I should just find out for myself. What’d’ya think about that, Stutterbug? I’ll bet little Zimmy over there can’t even grow pubes yet, how’d you like a taste of a _real_ dick?”

"I don't- Red, I ca- please, I-"

"Please? Well if you're begging for it so hard I can't just leave my poor little cousin hanging now can I? Get over here."

She meekly crawled over to Red. She shook so hard that she nearly collapsed every time she moved.

"Consider this a lesson, for both of you. _You_ " he grabbed his youngest cousins chin and angled it up so she was looking at him. "Are gonna learn how to suck a _real_ dick. And " he glanced over at Zim. "Are gonna learn what it looks like when a real man fucks your sister's face. Got it?"

Both siblings nodded meekly and Red lowered his pajama pants just enough to let his cock out. Perversely, instead of just making his youngest cousin open her mouth and blow him, he rubbed his cock against her cheek for a minute, using her hot salty tears as lube.

He hadn’t been wrong on all counts, exactly. Zim was barely half Red’s height, and that size difference was reflected twofold in their dicks. Considering that Zim was (somehow) taller than his sister, Red’s cock, standing rock-hard and at attention, was incredibly intimidating.

“Open your mouth. That’s it, take it all in. Hollow out your cheeks, and watch the chompers, kid. Don’t forget who’s gonna come running if I scream.”

Red had barely pushed the weeping head of his cock into his cousin’s mouth when he got impatient. Grabbing the hair on the back of her head, he shoved her face into his body, making her gag and choke as she was forced to deepthroat his length. 

“Aww, don’t be shy. Use your tongue, I’m sure you’ve gotten _plenty_ of experience with your big brother over there.”

She let out a gargled sob that made Zim's heart ache. He'd been rough with her before but nothing to this extent. He saw her twitch and wretch and-

He quickly grabbed her by the back of her night gown and yanked her off of Red's cock. She coughed and sputtered, drool running down her chin.

"What the _fuck_ Pipsqueak?" Red snapped.

"She was gonna puke if you kept doing that!" Zim snapped in response, cradling his sobbing sister.

"You know what? If you wanna protect your _poor, weak little sister_ , why don't you come do this yourself?" 

"What?!" Zim sputtered.

"You heard me. It's either you or her, kid. You've got thirty seconds to choose. The clock is ticking." Red sat back and watched Zim panic, with a sick sadistic smile.

Any inhabitations Zim might have had about putting his cousin’s cock in his mouth were overshadowed by the protective urge he felt when his sister, the _one person he truly loved_ , choked out a pained cough. 

He couldn’t let her suffer like that.

So Zim guided her gently to sit behind him, shooting an angry, hateful expression at his cousin, even when his chin was grabbed and shoved up against the guy’s cock.

“Well? You made your choice, Pipsqueak. Try not to choke on it and die, ‘kay?”

“I do this, and you keep _this_ awful thing out of her mouth, yes?”

“Yeah, sure, whatever. Now get to it, don’t blueball me, ‘cuz. Better hope you’re thirsty, with you two freaks here I haven’t been able to crank one out all week.”

Even with just the head of Red's cock in his mouth, Zim nearly puked. How the hell did his sister do this without gagging at the taste?

Zim tried to imitate what she had previously done to him, bobbing and twisting in a concentrated effort to just _get this over with._

"Shit, Pipsqueak, have you done this before? I didn't take you for a cock sucker but damn!" Red laughed, grabbing a fistful of Zim's hair and pushing him forward just as he had done to his sister.

Zim choked and coughed on his cock, but that only seemed to fuel Red's lust. He pulled Zim back and forth by the hair, using his little cousins face as a fleshlight. Zim was tempted to bite Red but he was terrified of what the consequences of that would be.

Zim breathed through his nose, trying to avoid gagging or choking too hard. His eyes welled up with the kind of tears that hurt when they spilled over, the taste and smell of his cousin’s sex burning themselves into his senses.

Red was quiet when he came, simply shoving Zim’s head down as far as he could with both hands and shooting a load of sticky, salty liquid down his throat.

He didn’t even bother letting Zim catch his breath, just kept hold of his hair and let himself twitch and leak into his cousin’s mouth until he started to go soft. 

Once he was done, Red simply let go of Zim, letting his body fall back on the hard wooden floor. 

“Shit, Pipsqueak, that was the best blowjob I’ve had in _ages_. Are you sure you haven’t been whoring yourself out when I’m not looking?”

"He’s not a whore!" His sister insisted. Red barked out s laugh.

"Shit, I think that's the first sentence you've said without stuttering!" Red exclaimed. 

"He's not a whore." She repeated, with far less conviction than she had the first time she said it.

"Yeah, yeah, whatever you say Stutterbug." Red laughed. "Hm. Y'know it doesnt seem fair for only one of you to take my load. You've _both_ been supremely fucking annoying this week so you both deserve a punishment."

"Hey! You said if I did that-"

"Yeah I know what I said. I'll keep my promise. I won't make her blow me. I never agreed to anything else though." He said, with a sinister smirk that made Zim and his sister both shiver.

Before Zim could fight, before he could do _anything_ , Red took the hem of his new victim’s dress in his fist and yanked it up, exposing the still naked, still _wet_ flesh beneath. 

“You’ve fucked her properly before, right?”

“How _dare_ you suggest you’d take what she _willingly gave_ to me...!”

“Oh, I’m not ~suggesting~ anything. I fully intend to dick her down right here, right now. Your mouth was a nice warm-up, but you should know _nothing_ beats real pussy. Even if it is your own flesh-and-blood.”

“Why you little—!”

“Or maybe for you two freaks, it’s _because_ you’ve got the same blood. I dunno, _cousin_ , you’re closer to her than I am, why don’t you tell me.”

Zim didn't know how to argue it.

If he really thought about it, he had to admit that her being his sister was a factor in his attraction to her. But it wasn't perverse in the way that Red was suggesting, it was far more... _pure_ than that.

It was romantic. He cared for her in a way that no other man in the world could. He loved her as her brother, teasingly, and annoyingly, and he loved her as her lover, fully, and lustfully. 

"Zim?" She whimpered, and Zim immediately took her hand. He thought about jumping up and hitting Red. He considered beating the shit out of him before he dared to fuck his precious little sister. 

But Red was bigger than him. He was stronger, and older, and no one would believe Zim if he said Red was the one who started it all. 

So he leaned down and kissed his sisters forehead (ignorring Red's scoff at the display of genuine affection) and whispered, "everything will be fine, just relax and it will be over soon."

She bit the inside of her mouth and nodded, holding Zim’s hand to her face and burying her nose in his arm as she braced for the oncoming intrusion. 

Red rolled his eyes at the very idea that anything his cousins, _a pair of siblings_ , could do sexually would ever be moral, or god forbid, _romantic_. 

_Zim_ had started this. _Zim_ touched her, her first. Red wasn’t doing anything wrong, because you can’t _break_ what’s _already broken_.

So he wasn’t gentle when he stuffed himself into her slimy hole. She muffled her screams in Zim’s sleeve, and offered no resistance when Red took her ass in his hand and shoved it up to his lap.

Her breathing was frantic an uncontrolled. 

"It hurts!" She whisper screamed. "It hurts, please stop it hurts so much!"

Zim stroked her hair, trying to comfort her as she winced and sobbed. His own eyes were watering, his heart ached for her and he wished that he could once again take her place and alleviate her pain.

"Shut up," Red groaned, digging his nails into her hips. "I'm not stopping now. And you can't tell anybody about this because no one will believe you." He seemed to find _extreme_ pleasure in that, in the knowledge that his cousins were free for him to use.

Zim felt his sister’s tears fall anew onto his lap when their cousin finally sheathed himself fully in her body. Zim could see her juices dribble out of her cunt, his cousin’s engorged girth pushing the fluid out like a syringe plunger.

A few short, experimental thrusts into the act and both parties involved were shaking and biting back screams. One from pleasure, one from pain. 

“Ffffffuck, that feels good! Shit, Stutterbug, you’re tight...guess you and the Pipsqueak...you’ve been holding out on me, huh? God, if I’d known you little perverts were _this_ fucked up, I would have done this years ago!”

"Don't speak to her like that!" Zim hissed, and before Red could respond his sweet little sister gently cupped his cheek and directed his gaze down at her. With every few words she spoke, Red would thrust into her, making her voice quiver and her eyes water.

"It's okay, Zim." _Thrust._ "Like you said." _Thrust._ "It'll be over soon." _Thrust._

Zim nodded and choked back tears. He hated himself for crying when he should be the one comforting her.

"Would you guys just shut the fuck up already? I'm never gonna cum if you keep saying dumb shit." Red groaned. He picked up his cousins legs and pulled them over his shoulders, fucking her with increased force that made her crying go from a steady trickle of tears to outright hiccuping sobs.

Red’s hand practically dwarfed her, the meat of his palm pressing against her mouth as a makeshift gag. He pushed her head painfully against Zim’s lap, putting just enough pressure on her skull and his legs that it was sure to bruise, and in the moment, that it _hurt_.

“Close your mouth, and keep it shut. Or do you want all of _this_ ,” Red said, emphasizing the last word with a particularly aggressive snap of his hips. “To be for nothing when someone hears you, and we get _caught_?”

Zim gently pet his crying sister’s hair, pushing down the impulsive desire to beat his cousin senseless, held back only by the knowledge that he couldn’t possibly win. 

“God, you’re so fucking tiny, you feel like a vice. Have you even hit puberty yet? Or did this little sicko come onto you even without it?”

Zim growled, but his rage-fueled retort was cut off by fear at his cousin’s next sentence.

“Fuck it, if I knock you up we’ll deal with it later.”

He wanted to puke. He wanted to scream. He wanted to kill his cousin right then and there before the bastard even got the chance to pull his pants up.

The thought of his sister pregnant with his cousins child was absolutely _vile_. He hated that he could see it so clearly. The deep, dark circles under her eyes, how greasy and limp her hair would get, the way she'd unconsciously scratch at her stomach, like there were bugs crawling just below the surface of her skin.

"Fuck, you're enjoying this aren't you, little whore?" Red hissed. She shook her head no but Red just pressed her harder against Zim's leg, making both of them wince.

"If you're not enjoying it then why are you so wet?"

She didn’t respond, just shuddered and shoved her face further into her brother’s comforting hold. Red was moaning under his breath at this point, biting his lip and muttering incoherent cusses and insults. His pace was erratic, brutal, _barbaric_. 

But for all his moaning and his filthy mouth, Red was again quiet when he came. His mouth hung open, tongue lolling out past his teeth as he kept himself buried in his youngest cousin’s tiny pussy. He kept her hips tilted up when he finally pulled his soft dick out of her. 

Zim was repulsed, even more so than before, when Red had the _gall_ to look disappointed when his cum started dripping out of his sister.

"Well. That was fun! See you guys at breakfast tomorrow!" Red pulled his pants up, unlocked the attic door and was gone, just like that.

Both siblings held still for a few moments, terrified that he would come back. Zim stroked his sisters hair and whispered incoherent apologies until she stood up. She padded over to the door, wincing with every step, and she locked it.

"We should have locked it when we went to bed." She said softly. She looked at Zim, still sweating and crying and rock hard and something in her shifted.

She walked back to her brother as quickly as she could and pulled him into a hug. Despite the fear, the hate, the _shame_ of it all, despite the uncomfortable stick of sweaty skin, the overwhelming stench of sex and sin, and the burning tears threatening to spill over yet again...the contact made it all seem better.

Zim wrapped his arms around his sister’s waist instinctively, pressing his forehead into the crook of her neck and letting her bury her hands in his hair.

“Zim...I...”

“Shh...we’re alone now, it’s ok...”

“No, Zim...I...I can _feel_ it...ugh, inside me...”

“Does it hurt?”

“Yes...”

“I’m so sorry...”

“Zim...I don’t...can you...I-I mean, I don’t want _him_ to be...who I _think about_ when there’s...y’know... _cum_ inside me.”

"Do...do you want me to...?"

" _Please?_ ”

Zim hated himself for still wanting to fuck her after all that they'd just gone through. But he couldn't say no to her, even under simpler circumstances. 

"Okay." Zim said, softly. He leaned forward until his sisters back hit the mattress and pulled away just far enough to kiss her on the lips. He went out of his way to rub her clit, a part of her that their cousin had severely neglected.

She whined, tension melting away at his touch. Her hands remained in his hair, gently brushing over the places where Red had tugged at it. As Zim felt his tears fall, he could have sworn his sister really _was_ an angel, her touch healing him in every way possible.

He wanted to give that feeling back to her.

So he kissed her gently, sweetly, as he pressed his cock into her. She sighed a sigh of relief, the cathartic sound easing the pain and reminding Zim of why he’d fallen in love with his sister in the first place. 

He hated himself for being so delighted when she kissed him back.

It wasn't by any means the first time they'd had sex. But it was, perhaps, one of the first times they truly made love. 

They held each other in the way that only two damaged hearts can. When Zim bottomed out in her, she whispered "I love you, I love you, I love you," over and over again. Like a chant.

Like a prayer.

He moved slowly inside of her, terrified of hurting her more than she already had been. She certainly didn't seem to mind the slow pace from the way her breathing became heavy and uneven.

She kept whispering into his ear, mindless repetition of the same three words. Zim echoed her sentiment, punctuating each declaration with a soft kiss to her neck or cheek. 

She came before him, her inner walls constricting and pulsing with her heartbeat. Zim’s name left her tongue in a barely-audible whisper as she did, and that was enough to spur his own orgasm.

Zim kissed her gently, an action driven by love and passion. He spilled himself into his sister’s body for what felt like the millionth time, losing himself in the feeling of flooding her body with his seed. 

He pressed his forehead to hers and held her face with both his hands, wiping away her tears with his thumb as they came down.

When he pulled out of her she winced. Zim, in spite of his exhaustion (both physical and emotional) pulled up his shorts and stood up to turn off the lights.

He stumbled blindly back to the mattress, where his sister was waiting with open arms. They didn't speak as they fell asleep. There was nothing they needed to communicate that couldn't be done simply by holding one another.

For a moment, everything felt okay. His sisters arms around him, a soft mattress underneath them, and their stomachs full of Christmas cookies, were all inherently good and pleasant things.

But he couldn't help dreading tomorrow.

**Author's Note:**

> The entire premise of this story is “what if Red was like 2 degrees more fucked up and also like 5 minutes more late in the Chapter 4 flashback”.


End file.
